A gas circuit breaker is used when it is required to break an excessively high fault electric current, a low leading (capacitive) current, low lagging (inductive) load current such as a reactor breaking, or an extremely small fault electric current in an electric power system. The gas circuit breaker mechanically separates a contact shoe in the process of breaking, and blows arc-extinguishing gas to eliminate arc discharge generated in the process of breaking.
The gas circuit breaker explained above has a puffer-type, which is currently widely used (for example, Japanese published examined Patent Application No. H7-109744 (hereinafter referred to as Patent Literature 1). The puffer-type gas circuit breaker has an opposing arc contact shoe and an opposing energizing contact shoe and a movable arc contact shoe and a movable energizing contact shoe arranged to oppose each other in a sealed container filled with an arc-extinguishing gas, and causes each of them to be in contact with each other or move away from each other by a mechanical driving force, so that the electric current is passed or cut off.
This gas circuit breaker includes a pressure accumulation space of which capacity decreases as the contact shoe moves away and accordingly the internal arc-extinguishing gas is pressurized and accumulated, and an insulation nozzle arranged to enclose both of the arc contact shoes to guide the arc-extinguishing gas in the pressure accumulation space to the arc. In the process of breaking, the opposing arc contact shoe and the movable arc contact shoe move away from each other, so that an arc is generated between both of the arc contact shoes. As the contact shoe moves away, the arc-extinguishing gas sufficiently pressurized and accumulated in the pressure accumulation space is strongly blown to the arc via the insulation nozzle, so that the insulation performance of both of the arc contact shoes is recovered, whereby the arc is eliminated, and the breaking of the electric current is completed.
A so-called tandem-puffer-type is widely used as a gas circuit breaker capable of effectively breaking any electric current from a small electric current to a large electric current (for example, Japanese published examined Patent Application No. H7-97466 (hereinafter referred to as Patent Literature 2)). In this gas circuit breaker, the pressure accumulation space is divided into two chambers of which pressurization mechanisms are different, in order to improve the breaking performance without increasing the driving energy. More specifically, the gas circuit breaker includes both of the spaces, i.e., a thermal puffer chamber and a mechanical puffer chamber, and generates a strong jet flow by pressurizing the arc-extinguishing gas by using both of the heating pressurization action and the mechanical pressurizing action.
When a large electric current is broken (interrupted), the arc discharge is at an extremely high temperature, and therefore, the ambient arc-extinguishing gas is heated, and with the thermal expansion of this arc-extinguishing gas and the flow into the thermal puffer chamber, the thermal puffer chamber is significantly pressurized. The pressure of this thermal puffer chamber generates a blowing force of the arc-extinguishing gas which is sufficient for eliminating the arc discharge.
On the other hand, when a small electric current is broken, the self pressurization action by the arc discharge is small, and therefore, the increase in the pressure in the thermal puffer chamber with this action cannot be expected. In such case, the tandem-puffer-type gas circuit breaker can also use the feeding of the arc-extinguishing gas from the mechanical puffer chamber to the thermal puffer chamber, and therefore, a blowing pressure for breaking a small electric current can be ensured.
In this case, in a case of an arc of a large electric current in the order of several kilo amperes, e.g., breaking of a fault electric current, the arc is not eliminated even at the zero point of the electric current unless it is after the distance between both of the arc contact shoes is sufficiently open and an appropriate flow channel is formed and after a sufficient blowing pressure is pressurized and accumulated in the pressure accumulation space.
However, in a case of an arc of a small electric current equal to or less than several hundred amperes, e.g., breaking of a low leading (capacitive) current break, the arc can be easily eliminated (extinguished) at the zero point of the electric current even it is immediately after both of the arc contact shoes are open and moved away from each other. Then, depending on the electric current phase, the time for which the arc continues becomes extremely close to zero, and the arc is eliminated immediately after the arc contact shoes are open and moved away from each other, and a recovery voltage is applied from a system while the distance between the arc contact shoes is extremely small. When the restrike (reignition) of the arc occurs between the arc contact shoes because of this recovery voltage, an overvoltage may be generated. The restrike of the arc means a breakdown phenomenon that occurs after a time equal to or more than one-fourth of the cycle elapses after the zero point of the electric current with a commercial frequency voltage.
The insulation breakdown between the arc contact shoes may jeopardize the reliability of the system device, and therefore, in general, a gas circuit breaker is required to have a quick insulation recovery property (characteristic) sufficient for avoiding the restrike of the arc. In order to satisfy the demand, in general, it is necessary to alleviate an electric field at the tip (end) of the arc contact shoe, or it is necessary to improve the speed at a point in time when both of the arc contact shoes open and move away from each other, and more specifically, it is necessary to improve the contact parting speed, thus ensuring quick insulation recovery between arc contact shoes.
However, when a higher speed is supported by increasing the operation force, there is a problem in that the size of the driving device becomes larger, or the weight of the movable contact shoe unit increases in order to increase the mechanical strength, and it is necessary to further increase the driving energy.
Therefore, a technique has been suggested to connect a driving device and a movable contact shoe unit via a fixed cam mechanism, and drive a link joined with the movable contact shoe unit along the shape of the groove of the cam, thus improving the speed after the contact parting (for example, Japanese Patent Application Laid-Open No. 2004-55420 (hereinafter referred to as Patent Literature 3)). A technique has also been suggested to provide a rotation groove cam between a driving device and a movable contact shoe unit, thereby reducing the moving distance of the movable contact unit and the movable unit at the driving device side and efficiently reducing the driving energy (for example, Japanese Patent Application Laid-Open No. 2002-208336 (hereinafter referred to as Patent Literature 4)).
However, a conventional gas circuit breaker involves the following problem, and solving this problem is desired.
(A) Temperature of Blown Gas
In a conventional gas circuit breaker, the arc-extinguishing gas of which temperature has been raised by the arc discharge is retrieved into a puffer chamber or a thermal puffer chamber, and therefore, the high temperature arc-extinguishing gas is blown to the arc discharge. As a result, the cooling efficiency for cooling the arc discharge is reduced, and the breaking performance may decrease.
(B) Effect to Durability and Maintenance Caused by the Temperature of Blown Gas
When the high temperature arc-extinguishing gas is blown to the arc discharge, the temperature around the arc discharge is also raised. As a result, the arc electrode and the insulation nozzle are subjected to high temperature and are likely to be degraded (deteriorated), and accordingly, it is necessary to frequently perform maintenance. This is contrary to the needs of the users who seek the improvement of the durability and the reduction of the maintenance.
(C) Electric Current Breaking Time
Further, it takes a certain amount of time to increase the pressure in the puffer chamber and the thermal puffer chamber. For this reason, it may take a long time to complete breaking of the electric current. The gas circuit breaker is a device for quickly breaking an excessively high fault electric current in an electric power system, and therefore, from the perspective of the basic function of the gas circuit breaker, it is always required to reduce the time until the breaking of the electric current is completed.
(D) Driving Operation Force
In order to reduce the driving operation force in the gas circuit breaker, it is important to achieve the simplification of the configuration and reduce the weight. For example, in a tandem-puffer-type gas circuit breaker obtained by dividing the puffer chamber into two parts, additional components such as a diaphragm (partition plate) and a check valve, and therefore, the structure becomes more complicated, and the weight of the movable portion tends to increase. When the weight of the movable portion increases, a stronger driving operation force is needed in order to obtain the same separation speed. More specifically, in a conventional tandem-puffer-type gas circuit breaker, the configuration is required to be simplified in order to reduce the weight of the movable portion.
(E) How Gas Flows
Further, in the puffer-type gas circuit breaker for blowing the arc-extinguishing gas to the arc discharge, stabilization of the flow of the arc-extinguishing gas in the device is also regarded as important. In particular, in the tandem-puffer-type gas circuit breaker, the flow of the arc-extinguishing gas is likely to become unstable, and the improvement thereof is desired.
(F) Break Performance During High Speed Reclosing Operation
Further, in the gas circuit breaker, needless to say, the breaking performance during the high speed reclosing operation is required to be excellent, but in the tandem-puffer-type gas circuit breaker, the breaking performance during the high speed reclosing operation may be low, which has become a problem.
A gas circuit breaker according to the present embodiment is suggested to solve the above problems. More specifically, it is an object of the gas circuit breaker according to the present embodiment to provide a gas circuit breaker that reduces the temperature of a blown gas, improves the durability, reduces the maintenance, reduces the time it takes to break an electric current, reduces a driving operation force, stabilize the flow of an arc-extinguishing gas, and further, improves the breaking performance during high speed reclosing operation.
In order to achieve the above object, the gas circuit breaker according to the present embodiment is a gas circuit breaker for switching breaking and turning-on of an electric current, and is characterized in having the following configuration.
(a) A sealed container filled with an arc-extinguishing gas,
(b) A pair of fixed arc electrodes arranged in the sealed container to be opposite to each other,
(c) a trigger electrode freely and movably arranged between the fixed arc electrodes and generating an arc discharge according to movement,
(d) a pressurization unit pressuring and increasing a pressure of the arc-extinguishing gas with pressurization means,
(e) a pressure accumulation unit in communication with the pressurization unit and accumulating the pressurized arc-extinguishing gas,
(f) the trigger electrode is open and close means for switching the pressure accumulation unit into a closed state or an open state, and the pressure accumulation unit is switched to the closed state in a first half of breaking of the electric current, and the pressure accumulation unit is switched to the open state in a latter half (a second half) of breaking of the electric current, so that the arc-extinguishing gas in the pressure accumulation unit is guided to the arc discharge.